The subject matter disclosed herein relates to reinforced articles, such as gas turbine engine components, and more particularly to reinforced articles which are resistant to cracking and/or delamination, and methods of making the same.
Gas turbine engines accelerate gases, forcing the gases into a combustion chamber where heat is added to increase the volume of the gases. The expanded gases are then directed toward a turbine to extract the energy generated by the expanded gases. In order to endure the high temperatures and extreme operating conditions in gas turbine engines, gas turbine engine components, such as turbine blades, are fabricated from metal, ceramic or ceramic matrix composite materials.
Thermal barrier coatings are applied to the surface of gas turbine engine components to provide added protection and to thermally insulate the gas turbine engine components during operation of the gas turbine engine at high temperatures. A thermal barrier coating has at least one protective layer and a bond layer. The at least one protective layer is applied to a substrate, such as a gas turbine engine component, via the bond layer. The protective layer is a ceramic material and can include multiple layers.
Cooling holes are incorporated into gas turbine engine components in order to allow for more efficient operation at higher operating temperatures. Cooling holes are drilled into the gas turbine engine component, for example, using laser drilling. In gas turbine engine components having a thermal barrier coating, the cooling holes extend through the at least one protective layer, the bond layer and the substrate of the gas turbine engine component.
During operation of the gas turbine engine, the areas surrounding these cooling holes undergo cracking and/or delamination. The process of drilling the cooling holes results in degradation at the interface between the bond layer and the substrate and/or the bond layer and the at least one protective layer. In addition, the hot gas environment in gas turbine engines results in oxidation of the bond layer and formation of a thermally grown oxide (TGO) layer. The TGO layer creeps into the at least one protective layer as a result of shear stress due to, for example, centrifugal load or mismatch of thermal expansion between adjacent layers or between a layer and the substrate. The formation and creep of the TGO layer causes cracking and/or delamination at the interface between the substrate and the bond layer and/or at the interface between the bond layer and the at least one protective layer, thereby increasing the frequency of repairs and/or reducing the overall lifetime of the component.
It is therefore desirable to provide reinforced articles having improved cracking and/or delamination resistance, and methods of making the same, which solve one or more of the aforementioned problems.